This article urges a fundamental change in the administration of criminal justice. It calls for an active role for trial courts in determining the admissibility of police-generated lay witness testimony. The article focuses on what I call “police-generated witness testimony,” by which I mean confessions, police informants, and eyewitness identifications. These types of testimony are leading causes of wrongful convictions. The article shows that heavy-handed tactics by the police have a tendency to produce false evidence of these types, especially when the individuals being questioned by police are particularly vulnerable such as juveniles, or those who are intellectually disabled or mentally ill. It also demonstrates that there are procedural best practices that the police can follow to reduce the dangers of false evidence. The most important feature of the article is the proposal that courts take an active role in ensuring the reliability of criminal trials by invoking their gatekeeping responsibilities in screening police-generated evidence by holding pretrial reliability hearings. Current constitutional doctrine fails to exclude patently unreliable police-generated testimony. However, Rule 403 gives the courts broad discretion to exclude evidence on the grounds that its potential to mislead the jury substantially outweighs its probative value. State due process law can also be invoked. Reliability hearings for lay witness testimony already exist for some types of evidence in criminal cases (mostly defense evidence), and they are also clearly required for expert scientific evidence. Moreover, effective gatekeeping is consistent with the objectives of the rules of evidence, not to mention ethical requirements that judges secure the integrity of the trial process.